Particulate matter (PM) is microscopic solid or liquid matter suspended in atmosphere. Larger particles are generally filtered in the nose and throat via cilia and mucus, but particulate matter smaller than about 10 micrometers can penetrate the deepest part of the lungs such as the bronchioles or alveoli, and settle in the bronchi and lungs. Finer particles with a diameter of 2.5 micrometers or less, i.e. PM2.5 particles, are deadly air pollution due to their ability to penetrate deep into the lungs and blood streams. Very small particles (<100 nanometers) such as particles emitted from modern diesel engines and soot particles may pass through the lungs to affect other organs. These nanoparticles may be damaging to the cardiovascular system, as they can pass through cell membranes and migrate into other organs, including the brain. The effects of inhaling particulate matter on the health of humans and animals include asthma, lung cancer, respiratory diseases, cardiovascular disease, permanent DNA mutations, heart attacks, premature delivery, birth defects, low birth weight, and premature death.
Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary room temperature. Although not acutely toxic, anthropogenic VOCs are harmful to human health in long term. Long-term exposure to volatile organic compounds (VOCs) in the indoor environment can contribute to sick building syndrome. In offices, VOC results from new furnishings, wall coverings, and office equipment such as photocopy machines, which can off-gas VOCs into the air. Leukemia and lymphoma can increase through prolonged exposure of VOCs in the indoor environment. The aromatic VOC compound benzene, emitted from exhaled cigarette smoke, is labeled as carcinogenic and is ten times higher in smokers than in nonsmokers. EPA has found concentrations of VOCs in indoor air to be 2 to 5 times greater than in outdoor air. Studies have shown that individual VOC emissions by themselves are not that high in an indoor environment, but the indoor total VOC (TVOC) concentrations can be up to five times higher than the VOC outdoor levels.
Ozone is another air contaminant. Combustion of fossil fuels can emit pollutants as ozone precursors, which, when irradiated by UV rays, produce tropospheric ozone near the Earth's surface. In China, fossil fuel burning raises ground level ozone far above background levels. Ground-level ozone may harm lung function and irritate the respiratory system. Exposure to ozone and its precursor is linked to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems. Long-term exposure to ozone may increase risk of death from respiratory illness. Ozone can also be present in indoor air pollution, partly as a result of electronic equipment such as photocopiers. Because of the strongly oxidizing properties of ozone, ozone is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques, a form of heart disease.
CO2 per se is not an air contaminant, but it can indirectly reflect the level of indoor oxygen level. As a rule of thumb, the higher the indoor CO2 level, the lower the indoor oxygen level. CO2 is typically found in outside air at concentrations between 300 and 500 PPM and is exhaled by human beings at an approximate rate of 0.01 CFM per person for a person doing typical office work. Variations in the number of people in an office compared to the amount of outside air supplied into the building can easily increase indoor CO2 levels to between 500 and 2500 PPM. As such, CO2 can be used as an excellent indicator of proper ventilation on a per person basis sometimes referred to as the CFM of outside air per person since the level of CO2 in a space is directly related to the number of people in a space divided by the rise in CO2 from outdoor levels. Human beings are unaffected by relatively high levels of CO2 such as up to 5000 PPM, which would be extremely rare to find in any building of ordinary construction. However, inadequate oxygen supply may cause generalized hypoxia, the symptoms associated with which range from fatigue, numbness, tingling of extremities, to nausea and anoxia. In severe hypoxia, or hypoxia of very rapid onset, ataxia, confusion, disorientation, hallucinations, behavioral change, severe headaches, and reduced level of consciousness may be the symptoms.
Today, people spend 90% of their time indoors, and indoor air quality/comfort is essential for the occupants' well-being. Accurate monitoring the indoor levels of PM2.5 particles, CO2 and TVOC, followed by “smart” and efficient ventilating of the indoor space, is no doubt the most important goal of many industrial researches and developments.
Advantageously, the present invention provides a ventilation system, a HVAC system comprising the ventilation system, and a process of using the ventilation system for improving air quality, that can meet the need as described above.